In modern work vehicles, hydraulic circuits are used to power the hydraulic cylinders that manipulate work implements. Such systems may use pumps of the variable displacement type which control the flow rate of hydraulic fluid via manipulation of their displacement volumes. A displacement control valve is used to determine the direction of fluid flow to accomplish the work desired, i.e., for example, to extend or retract the hydraulic cylinder. The displacement control valve is also used to allow free flow of fluid so as to minimize pressure generated, i.e., to enable floating; an operating mode in which an implement rests on and follows the contours of the earth as the work vehicle is propelled along the ground.
In an overwhelming majority of hydraulic systems for work vehicles, hydraulic cylinders generate less power and use less fluid in moving to a retracted position than they do in moving to an extended position. Although charge pumps are used to make up volume differences in the fluid medium as the cylinder moves from a retracted position to an extended position, the risk of cavitation due to an inadequate supply of fluid to the variable displacement hydraulic pump is not entirely eliminated. Usually, the risk of cavitation is further reduced via the use of sophisticated and, generally, expensive valves.